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off-line SMPS const current 1-2kW

W

Winfield Hill

Jan 1, 1970
0
legg wrote...
Sorenson sold the Xantrex product under it's own brand name, even
before it was bought-out by Xantrex. They never designed a HF unit
in-house to meet that form-factor.

That would explain the resemblence. My point was that Sorensen
has repair manuals with schematics, whereas Xantrex does not.
This policy just caused me some more difficulty when a Xantrex
supply I shipped to Germany failed last week.

Thanks,
- Win

whill_at_picovolt-dot-com
 
T

Terry Given

Jan 1, 1970
0
Its going to be a BIG unit, you might find a transformer hard to come by
as
its not really very big. I am holding in my left hand a 150kHz transformer
for a 2500W output power dc-dc converter, running from 16Vdc (yep, 16V - a
24V battery getting a beating), while I type this post. that dc-dc converter
had a 400V output, and the transformer is a toroid with a really sexy 2-turn
winding that occupies almost the entire winding area (all 4 surfaces); 400V
winding is about 40 turns. remove meaty copper "primary", replace with
suitable HV primary and voila. This dc-dc was a single bridge (modular, for
a mere 2kW? pah!) with universal input voltage PFC
Hmm.. it's well within the size range of SMPS cores that I see. The
larger ones (a few inches on a side) ought to be good for around 10kW.
This is relatively high voltage at reasonable current so it's not like
it has to be wound with bus bars.

there have been more papers written on "optimum" transformer design than I
care to recall. the upshot is: if operating as a transformer (rather than an
energy storage inductor, as in a flyback converter) then the only constraint
on power throughput is heat removal. core size and maximum allowable flux
density set a lower bound on the no. of turns, other than that the sky's the
limit.

I went to an interesting seminar run by Ed Bloom a decade or so ago, Ed went
through an "optimum" transformer design, and theoretically squeezed several
kW thru a tiny pot core. as long as it doesnt fry, push it harder.

The earlier comments re. input & output filtering are relevant, but at 2kW
this is not too much of a problem, if you can design your own magnetics.
input PFC is almost mandatory, but you could probably get away with a crude
approach (eg series charge, parallel discharge etc) or even just use a 3%
line choke (heavy). three-phase is better of course.
Of course 1-2kVA 60Hz transformers are reasonably small, relatively
cheap and common.

yep, and easy. The problem I always run into when I think about building
myself a monster psu (it happens every year or so) is that I cannot justify
the expense - time mostly, but money too. any PSU project really worth doing
tends to be costly, so I usually wait for people to pay me to do it.

BTW, what about a mini-SKiiP from semikron, driving a three-phase coaxial
power transformer & bridge rectifier, feeding an LC filter. I re-designed a
10kW one of these a few years ago; their transformer used some 80mm dia
cores (about 4 per leg) and was designed for an LVDC plating supply. making
the transformer was a breeze, and the control electronics was trivial too -
phase shift the other two legs wrt the 1st. switch IGBTs at about 8kHz, and
100kW is a breeze; drop Fsw to 4kHz and build a 1MW supply.......yeah the
magnetics are bigger at 8kHz, but still about 100 times smaller than 60Hz

Win's idea is best - go buy one.

If you just want to generate offensively large currents, go buy a grunty
toroid, with a decent hole thru the middle. drive it from a variac, and use
a shorted single turn 2ndary to get lost of amps. very handy for checking
exposed metalwork earth straps on big stuff (earth straps typically must
carry full rated fault current for 1-2mins without dying - for a 660A 415V
drive, thats a lot of amps)
 
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